Short-circuiting and retrieving apparatus for rheostats.



L. 8 H. L. BRADLEY.

SHORT CIRCUITING AND RETRIEVINGAPPARATUS FOR RHEOSTATS.

' APPLICATION FILED JULY I8 19I3. 1,148,656.

Patented Aug. 3, 1915.

liiiiQZtT-QERGUITXNG AND lit-ET 'EIEVING APFARATU'S F031, RI-IEDSTAT3.

mum-i. m

7 Medication of Letters Eatent.

L pplication filed. July 13, 1913.

To all who m may concern:

Be it known that we, Linton BRADLEY and HARRY L. BRADLEY, citizens ofthe United States, residing at Milwaukee, county of Milwaukee, antiState of Wisconsin, have invented new and. useful improvements inShortfiircuiting and Retrieving Apparatus for Rheostats, of which thefollowing is s specification.

Our invention relates to improvei cuts in short circuiting andretrieving apparatus for rheostats, with particular reference to thatclass of rheostats in which compressible resistance columns areemployed, the resist? ance being varied by varying the pressure.

In connection with the use of automatic motor starters, a demand for astarter has developed in which the rheostut will protect the motor atall times anti uncler all contlitions when used in combination withreversing switches, dynamic braking systems and special control systemsusing the so-culled operator switch or master switch.

The object of our invention is to provide o such a starter which will bequick acting,

which will make the necessary resistance changes more rapidly than it ispossible for the operator to move the reversing switch, or any lever bywhich is operator may change the working circuits of the motor,

wherehy the above mentioned demanrl may he fuliy satisfied.

It will he understood that if a motor starter is connected with areversible motor, it is desirable anli perhaps essential. that when thereversing switch is thrown intothe reverse position with the motorrunning at full speed, the starter shall immediateiy insert resistancein the power circuit to keep the flow of current within safe limitswhile the motor is being brought to a stop, after which the resistanceinterposeu the starter should he gradually removeol so that the motormay he brought up to the required speed in the reverse (iirection. Ourinvention contemplates the provision of automatic means foraccomplishing these results in connection with a starter having acompression rheostat, by removing the pressure from the resistancecolumn or columns as soon as the required speeri of the motor isattained, said columns having been firs cut out from the circuit or" themotor or at least removeci from the circuit of the motorh" shunting thecolumns from such circuit. this acoouiplieheu in known in common use tothose fan Patented Aug. 3, 1191i Serial No. 7 79,694.

our improved apparatus by means of a mag netic switch, and it istherefore only neces sary to open this switch in order to insert therequire& resistance into the circuit, since the pressure has beenpreviously removecl from the columns, thereby restoring their resistanceto maximum. The time requireci for opening the magnetic switch is soshort that the resistance may invariably he ins sorted into the powercircuit hefore any change of motor connections can be con pleted by theoperator, no matter how careless he may he.

The drawing is a diagrammatic illustra tion of our invention associatedin controlling relation to an electric motor. The-var; ous switch hoardelements are of well with this art, and they are-therefore laws 5trateci conventionally.

Compressihlc resistance columns 1 pinerahly composed of graphite tliskslar to those (lescriliecl in our former n for a resistance device,Number 100 (iatecl March 4th, 1913. The resistor. these columnsdecreases under pressure. our improved. construction, pressure is Ipliecl to the columns by trcnsnoittin mo from the plunger 2 of solenoid3, enrol hell. crank 4 andi en equalizing plate or 5, having universaljoint connection with one arm of the hell crank arr-a" to hear uponmovable eiectroeies Z pass into the tubes anrl hear against the ends ofthe graphite colonies An electrocle is is connected with lo enci ofplunger 2 by a push reel; 15?, uni the plum 2 completes its downwarfi meement, this electrode 14 makes contact "with electrode 15, connecting upthe winning of magnetic. switch 17 in circuit as herein tierclescribetl.When magnetic switch is energized, its plunger 18 moves upwardly untilits cross bar 19 connects contact p i 20. This short circuits thetubes 1. 1 un- 18 is proviciecl with a rod 21, adaptetl, when theplunger is lifted, to actua e a ro silient switch "bar 22 which controlsthe cuit of thcsolenoicl 3 at contacts 23. The upwarol movement of theplunger 18, therefore, not only short circuits the columns 1, but alsodisconnects the energizing circuit of solenoid 3, allowing spring 25 toretract hel crank 4c, raise solenoid core 2 to normal cleener izegiposition, and relieve th pressure upon the columns 1.

The elements above described are connected up with the motor circuit andoperate as follows:It will be observed that the winding of rheostatsolenoid 3 is connected through contacts 30 and bar 31- of acceleratingrelay 32 with blade 33 of the reversing switch 3 and through clip 35 tothe side of the line. Electrodes 7 and 15 are connected through thewinding of accelerating relay 32 with switch blade 33 of the reversingswitch. Upon closing the line switch 36, the path of the armaturecurrent of the motor can be followed from the positive side of the linethrough series motor field 37, circuit breaker 38, switch blade 39,pivot clip 40, the armature 11, resistance tubes 1, winding ofaccelerating relay 32, switch blade 33 and circuit breaker 43, to theside of the line. In the construction shown, the motor illustrated is acompound motor having both shunt and series fields. This is notessential to our invention, the device will work equally well with asimple shunt or series motor. The current for the shunt field passesfrom the side of the line, through series field 37, circuit breaker 38,clips and 46, shunt field 4:7, and clip 48 to clip 35, circuit breaker43 to the side of the line. The circuit of rheostat solenoid 3 is fromswitch blade 39, through clips 50 and 51, contact electrodes 23, switchbar 22, the winding of solenoid 3, contacts 30, and connecting bar 31 ofthe accelerating relay to switch blade 33. Upon closing the line switch36, plunger 2 of solenoid 3 will be drawn downwardly and its motiontransmitted through the bell crank 4 to compressthe resistancecolumns 1. This gradually reduces their resistance with consequent increase of current in the armature circuit until a point is reached atwhich accelerating relay 32 lifts the connecting bar or disk 31 andopens the circuit of solenoid 3, causing a momentary cessation ofpressure increase upon columns 1 with a tendency to decrease thepressure already attained. The motor,

' however, continues to accelerate and its increasing counterelectro-motive force, together with any diminution of pressure upon thecolumns, reduces the current until relay 32 again closes, whereuponrheostat solenoid 3 again acts to produce further pressure upon thecolumns 1. This alternate action of the solenoid and accelerating relaywill be rapidly repeated until solenoid plunger 2 is drawn downsufficiently to bring electrode 14 into contact with electrode 15, thusclosing the circuit through the winding of magnetic switch 17, thecurrent now flowing from the lower contact 23 through the winding ofswitch 17, through contacts 14L and 15, to the side of the line throughac celerating relay 32. But as soon as magnetic switch 17 is energized,its plunger 13 draws upwardly until bar 21 engages and lifts switch bar22, thus deenergizing the solenoid 3. The tubes 1 andrelay 32 have inthe meantime been short circuited by the upward movement of bar 19 toconnect electrodes 20, thereby allowing current to'flow from the side ofthe line between the armature ll and columns 1 directly to the side ofthe line represented by switch blade 33. It is not essential that theaccelerating relay 32 be shunted from the circuit, but this ispreferably done, and with electrode 20 connected below the relaywinding, it is obvious that said relay will be short circuited. \Vhenthe rheostat solenoid 3 is deenergized by breaking its circuit atcontacts 23, this would also deenergize magnetic switch 17 but for thefact that when the plunger 18 of the magnetic switch is lifted, contactslet and 15' are bridged from the winding of magnetic switch 17 throughbar or plate 19 and contact 20.

The rheostat solenoid 3 is comparatively large and possessesconsiderable magnetic and mechanical inertia. By removing it from themain circuit and permitting it to deenergize as soon as the requiredmotor speed has been attained, we secure the advantages of. economy incurrent, avoid injurious and unnecessary heating of the solenoid andgive it an ample retrieving interval, thus insuring restoration of theresistance units to a condition of minimum compression and maximumresistance before any change in the running conditions of the motor willbe required. It is therefore evident that whenever the reversing switch34: is operated, the smaller and quick'aeting magnetic switch 17 will bedeiinergized the moment that switch blade 33 lifts from contact 35, thuspermitting switch 22 to close contacts 23, whereupon any movement ofswitch 34- which either brings blade 39 to contact 48 or blade 39 tocontact 15 will again close the circuit through rheostat solenoid 3, andthe cycle of motor starting.

operations above described will again be performed.

A companion application bearing even date herewith, filed July 18, 1913,Serial No. 7 7 9,695, shows and describes some of the featuresillustrated in this application with claims for an alternative structuredesigned to accomplish the same general purpose sought to beaccomplished in the apparatus herein described. In the companionapplication, however, the construction'is such that the shunting of theresistance columns and rheostat solenoid is dependent on the conditionof the current-passing through the resistance eolumns,'whereas in thisapplication, it is dependent upon the attainment of a predetermineddegree of pressure upon such columns.

WVe claim 1. The combination with a compressible rheostat,-of acompressing lever, an electromagnetic device having a: movable membermechanically connected with said lever, and additional electromagneticmeans for cutting out said device when said lever has movedapre-determined distance.

2. The combination with a main electric circuit, of a compressibleresistance member, means for establishing said circuit through suchmember, electro-magnetic means for compressing said member,electro-magnetic means for prolonging the period of increasingcompression, and separate electromagnetic means for deenergi/ ing thecompressing means when maximum pressure 15 at tained.

3. The combination With a main circuit, of a compressible resistancemember, means for compressing the same, and electro-magnetic means forrelieving said member of pressure and removing it from the main circuit'during the final operation of the compressing means. I

4. The combination vith a main circuit,

of a compressible resistance member, means i for compressing the same,.ad electromagnetic means for relieving" said member of pressure andremoving it rom the main circuit during the final operation of the compressing means, said electro-magnetic'means comprising a solenoid, ashunt switch for the Inain circuit adapted to be operated by thesolenoid when energized, and means for utihzing the compressmg means toclose a CH- cuit through the winding of said solenoid, I

said solenoid being also adapted to maintain its energizing circuitindependently of the compressing means.

5. The combination witha main circuit,

' the magnetic switch.

6. The combination with a main circuit, of a compressible resistancemember, means for compressing the same and separate electro-magneticmeans for automatically removing it from the main circuit after apredetermined compressing movement has taken place.

7. In an electric current controller, the combination with a mainc1rcu1t,of a resistance medium, means for producing pressure on saidmedium, and means for removing said medium from said circuit at apredetermined stage in the operation of the pressure,

producing means, and means for automaticaly relieving said resistancemedium from pressure after it has been removed from said circuit.

In testimony whereof we atfix our signatures in the presence of twowitnesses.

LYN DE BRADLEY. HARRY L. BRADLEY.

Witnesses:

C. J. CAnLsoN, P. W. KAUFMANN.

